These are pets. They give different abilities.
Dragon-Attacks enemies from close up. They get better as you level.
Dog-Attacks enemies from close up. They have they're own level ups.
Firebird-Attacks enemies from far away, They get better as you level.
Thunderbird-Attacks enemies from far away. They have they're own level ups.
Builder-Give him instructions and he'll build for you while you do something else.
Zombie-Infects players, including you, with a zombie transformation.